16 THE SALTON SEA. 



Lieutenant Emory marched across the basin in the latter part of 1848 and seems to 

 have reached the shore of the Salton Lake.* 



Major Heintzleman, commandant at Yuma, visited the mud volcanoes near Volcano 

 Lake in 1852, and these were afterwards visited by John LeConte* and others. 



The Williamson expedition of 1853, in which the late Professor Blake took part, is 

 dealt with exhaustively elsewhere in this volume, and since that time our knowledge of 

 the Colorado Desert has been gradually added to from many sources. 



THE COLORADO RIVER AND ITS DELTA. 



The Colorado River, carrying its heavy burden of silt toward the sea, has been the 

 dominant factor during recent geological times in upbuilding and molding the region 

 under consideration. 



Emerging from a succession of small canons and inclosed basins, a short distance 

 below its junction with the Gila, it has spread its load over a vast area and in course of 

 time has built a broad barrier across the Gulf, and so isolated the two basins which now 

 constitute the major portion of the Colorado Desert from the sea. 



The seasonal change of volume in the flow of the river is in itself favorable to the rapid 

 upbuilding of this barrier, for the mud-laden and comparatively late spring run-off from the 

 mountains of Wyoming and northern Colorado reaches the flat lands of the Delta at a 

 time when the growth of annuals is well advanced, and as a consequence the overflowing 

 water is retarded, its erosive power checked, and its load of silt evenly and quietly laid 

 down. 



So rapidly is this building going on that there is good evidence that the mouth of the 

 river has been brought several miles farther south within the last 40 years. ' 



Such rapidity of upbuilding and the very character of the stream itself and the enor- 

 mous burden of solid material which it carries yearly to the sea almost warrant us in 

 assuming that the Colorado has been by far the most potent factor in working topographical 

 changes in the region during recent geological times. 



THE MAIN DELTA BARRIER. 



From the point of the Algodones Sand Hills at the head of the Delta to the small 

 outlier of the Cocopah Mountains known as the Cerro Prieto the distance is about 35 miles, 

 and a line drawn between these two points represents roughly the crest of the Delta dam 

 which separates the Salton Basin from the Gulf. This crest-line falls from about 110 feet 

 above sea-level at the Algodones to 30 feet at the foot of the Cerro Prieto, and the present 

 course of the Colorado River lies a little to the southeast of it. 



The bed of Volcano Lake, at an elevation of about 28 feet above sea-level, no doubt 

 represents part of the last spillway over this dam and may be taken as indicating the 

 water-level of the Salton Lake at its last complete filling. 



Gradients are so low and the growth of vegetation on the Delta so rapid that drainage 

 channels are not very strongly marked or permanent, quickly becoming obliterated when 

 unused, or surviving only as detached ponds or sloughs. It is fairly evident, however, 

 that the New River and the Hardy, which together form a continuous channel across the 

 barrier, falling in both directions from a meeting-point near the foot of the Cerro Prieto, 

 have also formed such a spillway; and the bed of this channel at its highest point lies at 

 practically the same level as the bed of Volcano Lake. 



' Notes of a military reconnoisance from Fort Leavenworth in Missouri to San Diego in California, by W. H. 



Emory, Washington, 1848. 

 » American Journal of Science and Arts, vol. xix, May 1855. 

 ' H. T. Cory, Irrigation and River Control in the Colorado River Delta, Transactions of American Society of 



Civil Engineers, vol. ixxvi, pp. 1204 to 1571. 1912. 



